Friday, June 19, 2009

Black Saturday

On Saturday 7th February 2009 the worst bushfires in the history of Australia cut a blazing swathe of destruction across the State of Victoria. More than 170 people lost their lives, over 2000 homes were razed and people from all over Australia were stunned by the enormity of the disaster.

The Lead Up

Most of Victoria has suffered a decline in rainfall over the last decade or so. In fact many areas, including Melbourne itself, have experienced below average annual rainfall over the last twelve years often resulting in tinder dry summers.

However the summer of 2008/2009 began on an optimistic note with good rains falling over much of Victoria and South Australia. This encouraged a growth spurt in the vegetation pattern across the area.

Then the rain abruptly stopped, temperatures rose and much of south-eastern Australia, including Victoria, found itself in the grip of a rolling heatwave that persisted across the area from mid January.

The Days Before

After two weeks of record-breaking temperatures and no rain, Victoria was tinder dry with the recent December growth producing an increase in the available bushfire fuel.

Unlike other notable heatwaves of the past there was little respite, with high temperatures persisting for nearly two weeks from mid January.

Numerous temperature records were broken across Victoria, with many centres recording their highest ever temperatures between the 28th and 30th January. Over the five consecutive days from 27th to 31st January inclusive maximum temperatures were 12-15C above average across much of Victoria – a very rare if unprecedented heat wave.

On Tuesday 3rd February, the computer simulations began predicting whatboth meteorologists and fire-fighters feared most. A strong cold front would move across south-eastern Australia on Saturday 7th February, preceded by hot, dry and gusty northwest winds and followed by a southwest change.

This would bring together all the ingredients of a major fire – abundant dry fuel, low humidity, strong winds, high temperatures and a wind change. The stage was set for disaster.

The Day Of The Bushfires

As the front approached Victoria on the morning of the 7th, rising northwest winds sent temperatures rocketing and the humidity plunging, fanning existing fires into infernos that rapidly jumped containment lines. Burning embers were carried aloft and transported kilometres downwind only to fall to ground and start new fires in the tinder-dry scrub.

Large tracts of central Victoria became raging firestorms that devoured everything in their path as temperatures again reached, and then surpassed, the records set only a few days before.

Melbourne’s temperature peaked at 46.4C, well above the longstanding record of 45.6C set on the day of the infamous Black Friday fires of January 13th 1939.

Smoke from the fires was clearly visible from space as this NASA image shows. Smoke was streaming out many kilometers from the fires out across the western parts of the Tasman Sea.(Click image to enlarge)

As the front moved across Victoria during the afternoon winds abruptly swung to the southwest, adding another dimension in unpredictability to the blazes.

The situation remained completely beyond control until temperatures fell overnight and the winds began easing. It was only then that the total devastation produced by the fires began to be understood.